Incorrect flow rates can cause incorrect critical measurements, unreliable steam and water sample analysis system (SWAS) performance and damaged equipment. Automating sample flow control on your SWAS can help you meet plant process needs without high personnel costs and metric concerns.

Importance of Properly Maintained sample flow

Power plants that frequently cycle or have sliding pressures often require technicians to manually adjust the pressure element in their sample panels. Making these adjustments is important to maintain proper sample flow and sample velocity.

However, many plants experience reduced staff resources, driving the need to automate these tasks for plant safety and staff efficiency. This situation is particularly acute during start-up and shut down cycles where consistent flow is critical to reliable analyzer measurements.

Most online analyzers require a particular range of sample flow to operate correctly. Power plant cycling directly impacts total sample flow and, by default, analyzer sample flows. Cycling operations can exacerbate sample temperatures, but analyzer flows fall into the pass/fail category.

Failure to maintain proper analyzer flow can result in false alarms and false information. Thus, flows are the most critical variable affected by power plant cycling.

Tools for sample flow automation

An automated flow controller helps plants automate their sampling points while maximizing staff capacity.

AutoVREL Flow Controller. An AutoVREL sample flow controller allows users to automate sample conditioning by controlling steam and water sample flow based on flow meter information. With the AutoVREL "smart" function, the operator sets the desired sample flow, and the system automatically adjusts to changes in the sample pressure.

Sample Sentry II. Besides sample flow control, the Sample Sentry II package offers additional features to control critical sample flows. The equipment provides sample parameter visibility such as sample temperature, sample pressure and cooling water temperature. Additionally, it is capable of automatically bypassing instruments used for flushing the sample line during start-ups.

Thermal Shut Off Valves. It's essential to consider adding thermal protection to the lines where the cooling water flow is interrupted or water temperature might experience excursions. Excessive temperature excursions or loss of coolant flow could damage sensitive analyzer probes or injure operators taking grab samples.

A Thermal Shutoff Valve (TSV) is a device that stops sample flow when the sample temperature is above a specific temperature. The valve provides some level of protection for downstream components that can't withstand high temperatures. TSVs can help protect operators and analyzers from potentially scalding water at temperatures above 120°F (50°C).

Sentry Equipment recommends using a TSV with the Sentry AutoVREL to protect your equipment. This layer of protection ensures the AutoVREL flow meter, analyzer probes and personnel remain safe from high-temperature samples.

By combining this equipment, you are protected when the VREL is left in a fully open position. The addition of the dry contact switch wired to the AutoVREL can add another layer of automation. If the TSV trips, the AutoVREL will automatically close.

Sample Sequencer. A sample sequencer is a steam and water sample automation system capable of automatically switching a maximum of eight sample streams between four analyzers. Time-sharing of analyzers lowers both acquisition and ongoing maintenance and reagent costs while providing performance advantages. It is capable of operating in a continuous or batch mode.

An example of this is the Sentry Sample Sequencer 5. This microprocessor-based system can electronically switch a maximum of eight sample streams between four analyzers.

By automating your sampling processes with one of these four methods, you are ensuring your plant remains at EPRI standards. You will also adequately protect your complete SWAS system from unnecessary downtime and damage.

Contact us at +1-262-567-7256 or complete our online contact form to discuss how Sentry automatic sampling systems can help you achieve safe, accurate and straightforward sampling results.